Operating lever for a valve train of an internal combustion engine

ABSTRACT

An operating lever for a valve train of an internal combustion engine comprises, on the valve-proximate end, a sliding shoe arranged between itself and an end of a valve stem of a gas exchange valve. 
     The operating lever is characterized in that it is configured as a chiplessly shaped sheet metal part and comprises in the valve-proximate region (2), a bottom wall (12) which is connected in an upwardly open U-shape to two side walls (5, 6), the bottom wall (12) comprises a downwardly open recess (13) for receiving the sliding shoe (14) which is inseparably retained in the recess (13), and spatial dimensions of the sliding shoe (14) and the recess (13) are matched to each other so that the sliding shoe (14) can freely execute a pivoting movement in the recess (13) caused by a displacement of the valve stem (11).

This application is a 371 of PCT/EP97/03664 filed Jul. 10, 1997.

FIELD OF THE INVENTION

The invention concerns an operating lever for a valve train of aninternal combustion engine with a sliding shoe arranged on avalve-proximate end between the operating lever and an end of a valvestem of a gas exchange valve, the sliding shoe being inseparablyretained in a downwardly open recess, and spatial dimensions of thesliding shoe and the recess being matched to each other so that thesliding shoe can freely execute a pivoting movement in the recess causedby a displacement of the valve stem.

BACKGROUND OF THE INVENTION

In an operating lever of the pre-cited type known from DE-GM 84 13 255,the sliding shoe arranged in the valve-proximate region between thelever and the gas exchange valve assures that wear in the region offorce transmission between the valve operating lever and the valve stemcaused by the surface contact between these parts is reduced to aminimum.

A drawback of this lever is that it is a cast structure and is thereforeexpensive to manufacture and has a large mass. A further drawback isthat the fixing of the sliding shoe in the lever is also verycomplicated. This is effected by a retaining pin which is anchored inthe lever and projects into the sliding shoe.

U.S. Pat. No. 5,535,641 discloses a chiplessly shaped finger levercomprising a bottom wall which connects two side walls to each other sothat, seen in cross-section, an upwardly open U-shaped lever is formed.However, this lever does not comprise a downwardly open recess and asliding shoe in the valve-proximate region.

SUMMARY OF THE INVENTION

The object of the invention is therefore to create an operating leverfor a valve train of an internal combustion engine which is easy tomanufacture, has a small mass and retains the sliding shoe inseparablyin a simple manner.

The invention achieves this object by the fact that the operating leveris configured as a chiplessly shaped sheet metal part and comprises inthe valve-proximate region, a bottom wall which is connected in anupwardly open U-shape to two side walls, the bottom wall comprises therecess for receiving the sliding shoe, the sliding shoe is retained bytwo clips which extend beyond the longitudinal extent of the operatinglever and are bent over beneath the bottom wall in the valveproximate-region while being spaced from each other at a distance whichis smaller than the spatial dimension of the sliding shoe. Besidesassuring the retention of the sliding shoe, these clips also serve as alateral guide for the lever above the valve stem.

The distance between the clips is chosen so that the sliding shoe can bemounted by an elastic widening of the clips. Further, the clips canstart from the bottom wall or from the side walls and be rigidlyconnected to the bottom wall or to the side walls in the bent-overstate. This connection can be achieved, for example, by welding andassures an operating lever having a particularly stable configuration.

According to a further feature of the invention, the recess isconfigured as a curved surface of a circular section, i.e. as asemi-spherical depression. But it is equally possible to configure therecess as a curved surface of a cylindrical section, i.e. as asemi-cylindrical depression.

The recess can be made by a non-chipping shaping procedure such asdrawing, stamping or pressing directly out of the bottom wall, or it canbe made as a separate component and retained in a correspondingreception of the bottom wall by pressing, soldering or gluing.

If the recess is configured as a curved surface of a cylindricalsection, i. e. as a semi-cylindrical depression, it is advantageous, forsimplifying the shaping of the semi-cylindrical depression, if thesurface to be curved to form the cylindrically shaped portion isseparated from the side walls, i.e. if it is connected to the operatinglever only at two opposing points in the region of the bottom wall.

The regions of the shaped portion which are separated for manufacturingreasons, i.e. the interrupted connection between the curved surface inthe cylindrically shaped portion and the side walls, can be joined toeach other again by welding or the like for obtaining more stabilityunder higher loading.

The sliding shoe is made as a pressed, drawn or sintered component andis advantageously provided with a wear-reducing coating, or it issubjected to a heat treatment to increase its hardness. In this way,friction between the sliding shoe and the valve stem is further reduced.

It can be advantageous to equip the sliding shoe with lateral guidecheeks for guiding the lever. Finally, for reducing friction, thereception of the sliding shoe is provided with a bore for the supply oflubricant.

The invention will now be described more closely with reference to thefollowing examples of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectional side view of a finger lever,

FIGS. 2 and 3 are bottom views of a finger lever in the valve-proximateregion, and

FIG. 4 shows a sliding shoe.

DETAILED DESCRIPTION OF THE DRAWINGS

The finger lever shown in FIGS. 1 to 4 is made without chip removal by ashaping procedure out of a sheet metal part and comprises the two endregions 1 and 2 and a central region 3. The end region 1 comprises abottom wall 4 from which two side walls 5 and 6 extend in an upwardlyopen U-shape over the entire axial dimension of the finger lever. Thebottom wall 4 possesses a downwardly open semi-spherical recess 7 whichrests on a support element, not shown.

A cam roller 10 contacted by a cam, not shown, is mounted for rotationin the central region 3 via a needle crown ring 9 on an axle 8. In theend region 2, there is arranged a gas exchange valve which opens upon apivoting motion of the finger lever caused by the cam. Thevalve-proximate region 2 likewise comprises a bottom wall 12 which isconnected in an upwardly open U-shape to the side walls 5 and 6. Thebottom wall 12 possesses a downwardly open recess 13 which is madeeither as a semi-spherical recess as shown in FIG. 2 or as asemi-cylindrical recess as shown in FIG. 3. A sliding shoe 14 isinserted into the recess 13 with its domed end in contact with therecess 13 and its flat surface in sliding contact with the gas exchangevalve 11.

As can be seen more particularly in FIG. 2, the size ratios between therecess 13 and the sliding shoe 14 are chosen so that a gap is formedtherebetween. This assures that, upon a pivoting motion of the fingerlever, the sliding shoe 14 can change its position within the recess 13without obstruction. To reduce friction, the recess 13 is provided witha bore 15 for the supply of lubricant.

As can be seen further in FIGS. 1 to 3, the sliding shoe is retained inthe recess 13 by two clips 16 and 17 which are bent over beneath thebottom wall 12 in the valve-proximate region 2. These clips 16 and 17start either from the bottom wall 12 as shown in FIG. 2, or from theside walls 5 and 6 as shown in FIG. 3 and provide a lateral guidance forthe lever. FIG. 1 also shows that the clips 5 and 6 bear only against apart of the bottom wall 12 so that in this respect, too, a free movementof the sliding shoe 14 within the recess 13 is assured. Finally, FIG. 4shows a sliding shoe 14 which is provided with lateral guide cheeks 18for guiding the gas exchange valve 11.

The invention, however, is not restricted to the described embodiment ofa finger lever. In place of the bottom walls 4 and 12, it is alsopossible to provide top walls from which the side walls 5 and 6 extenddownwards to give the finger lever the configuration of a downwardlyopen U-shape. Further, a reverse arrangement of the ball and thesemi-spherical recess is also possible, that is to say, a dome-shapedstamped projection can be provided on the finger lever to cooperate witha sliding shoe having a semi-spherical concave countersurface.

What is claimed is:
 1. An operating lever for a valve train of aninternal combustion engine with a sliding shoe (14) arranged on avalve-proximate end between the operating lever and an end of a valvestem (11) of a gas exchange valve (11), the sliding shoe (14) beinginseparably retained in a downwardly open recess (13), and spatialdimensions of the sliding shoe (14) and the recess (13) being matched toeach other so that the sliding shoe (14) can freely execute a pivotingmovement in the recess (13) caused by a displacement of the valve stem(11), wherein the operating lever is configured as a chiplessly shapedsheet metal part and comprises in the valve-proximate region (2), abottom wall (12) which is connected in an upwardly open U-shape to twoside walls (5, 6), the bottom wall comprises the recess (13) forreceiving the sliding shoe (14), and the sliding shoe (14) is retainedby two clips (16, 17) which extend beyond the longitudinal extent of theoperating lever and are bent over beneath the bottom wall (12) in thevalve-proximate region (2) while being spaced from each other at adistance which is smaller than the spatial dimension of the sliding shoe(14).
 2. An operating lever according to claim 1, wherein that thedistance between the clips (16, 17) is chosen so that the sliding shoe(14) can be mounted by an elastic widening of the clips (16, 17).
 3. Anoperating lever according to claim 1, wherein the clips (16,17) startfrom the bottom wall (12) or from the side walls (5,6) and are rigidlyconnected respectively to the bottom wall (12) or to the side walls(5,6) in the bent-over state.
 4. An operating lever according to claim1, wherein the recess (13) is configured as a curved surface of acircular section.
 5. An operating lever according to claim 1, whereinthe recess (13) is configured as a curved surface of a cylindricalsection.
 6. An operating lever according to claim 1, wherein that therecess (13) is made by a non-chipping shaping procedure of drawing,stamping or pressing directly out of the bottom wall (12) or as aseparate component which is retained in a corresponding reception of thebottom wall (12) by pressing, soldering or gluing.
 7. An operating leveraccording to claim 1 wherein the recess (13) is configured as asemi-spherical depression.
 8. An operating lever according to claim 5wherein the recess (13) is configured as a semi-cylindrical depression.9. An operating lever according to claim 1, wherein that the slidingshoe (14) is made as a pressed, drawn or sintered component.
 10. Anoperating lever according to claim 1, wherein that the sliding shoe (14)is provided with a wear-reducing coating, or subjected to a heattreatment.
 11. An operating lever according to claim 1 wherein that thesliding shoe (14) comprises lateral guide cheeks (18).
 12. An operatinglever according to claim 1, wherein that the recess (13) is providedwith a lubrication bore (15).